Population

The countries with the highest immigrant populations

Data: Pew Research Center; Chart: Axios Visuals

Robust immigration has buoyed the populations of the U.S., U.K. and other developed nations, keeping them from shrinking for now. But a number of aging countries don't have enough immigration to replace their population as their fertility rates continue to plummet.

The bottom line: The control of borders is a serious political problem, but experts are eyeing legal immigration as one solution to a future demographics challenge. As nations age, many will be short of workers to support social programs relied on by the older population.

Map: Where the world's population is growing and shrinking

The global population is expected to balloon to nearly 10 billion people by 2050, with Africa’s population doubling in that time and five of the world’s six inhabited continents growing significantly. Eastern Europe, on the other hand, is rapidly shrinking.

Data: United Nations World Population Prospects; Map: Lazaro Gamio/Axios